diff --git a/comfy_extras/nodes_compositor.py b/comfy_extras/nodes_compositor.py
index f66a9feab65..166b8ec4dcb 100644
--- a/comfy_extras/nodes_compositor.py
+++ b/comfy_extras/nodes_compositor.py
@@ -528,7 +528,9 @@ def execute(cls, layers: io.Layers.Type, compositor: io.Compositor.Type = None)
         raw_state = compositor
         state = parse_layer_state(raw_state)
         replay = bool(state is not None and tensors and state["inputs"] == fp)
+        canvas = None
         if replay:
+            canvas = state["canvas"]
             out = composite_from_state(tensors, state, alphas)
         elif tensors:
             canvas = document_canvas(layers) or canvas_extent(frames)
@@ -544,6 +546,8 @@ def execute(cls, layers: io.Layers.Type, compositor: io.Compositor.Type = None)
         ui_dict["compositor_layers"] = layer_refs
         ui_dict["compositor_inputs"] = fp
         ui_dict["compositor_bboxes"] = layer_ui_entries(frames)
+        if canvas is not None:
+            ui_dict["compositor_canvas"] = [{"w": int(canvas[0]), "h": int(canvas[1])}]
         if state_stale:
             ui_dict["compositor_state_stale"] = [True]
         return io.NodeOutput(out, mask, ui=ui_dict)
diff --git a/tests-unit/comfy_extras_test/compositor_node_test.py b/tests-unit/comfy_extras_test/compositor_node_test.py
index 3a24c4dffeb..b70148fda85 100644
--- a/tests-unit/comfy_extras_test/compositor_node_test.py
+++ b/tests-unit/comfy_extras_test/compositor_node_test.py
@@ -10,6 +10,7 @@
 import torch
 
 from comfy_extras.nodes_compositor import (
+    ImageCompositor,
     _layer_params,
     composite_from_state,
     expand_item_frames,
@@ -70,3 +71,43 @@ def test_uncovered_canvas_stays_transparent(self):
         assert out.shape[-1] == 4
         assert float(out[0, 0, 3]) == pytest.approx(1.0)
         assert float(out[3, 3, 3]) == pytest.approx(0.0)
+
+
+class TestCanvasEmission:
+    """execute must report the document canvas so the editor sizes itself to it
+    rather than to the max natural size of cropped/placed layers."""
+
+    def test_explicit_document_canvas_is_emitted(self):
+        # A small layer placed on a large explicit canvas: the editor must learn
+        # the 1280x1280 canvas, not the 200x150 layer size.
+        doc = {
+            "version": 1,
+            "canvas": (1280, 1280),
+            "layers": [
+                {"image": _solid([1.0, 0.0, 0.0, 1.0], w=200, h=150),
+                 "type": "raster", "x": 400, "y": 300, "z_index": 0}
+            ],
+        }
+        ui = ImageCompositor.execute(layers=doc).ui
+        assert ui["compositor_canvas"] == [{"w": 1280, "h": 1280}]
+
+    def test_replay_emits_saved_canvas(self):
+        tensor = _solid([0.0, 1.0, 0.0, 1.0], w=4, h=4)
+        doc = {"version": 1, "layers": [{"image": tensor, "type": "raster"}]}
+        fp = ImageCompositor.execute(layers=doc).ui["compositor_inputs"]
+        saved = {
+            "version": 1,
+            "canvas": {"w": 640, "h": 480},
+            "inputs": fp,
+            "layers": [{
+                "name": "a", "visible": True, "opacity": 1.0, "blend": "normal",
+                "flipH": False, "flipV": False,
+                "transform": {"x": 0, "y": 0, "w": 4, "h": 4, "rotation": 0.0},
+            }],
+        }
+        ui = ImageCompositor.execute(layers=doc, compositor=saved).ui
+        assert ui["compositor_canvas"] == [{"w": 640, "h": 480}]
+
+    def test_no_layers_emits_no_canvas(self):
+        ui = ImageCompositor.execute(layers={"version": 1, "layers": []}).ui
+        assert "compositor_canvas" not in ui